Re: [PATCH] msm: fix debug-macro.S build failure

[Daniel Walker <dwalker@codeaurora.org>]

On Thu, 2010-10-28 at 23:03 -0400, Nicolas Pitre wrote:
> On Thu, 28 Oct 2010, Russell King - ARM Linux wrote:
> 
> > On Thu, Oct 28, 2010 at 02:43:16PM -0400, Nicolas Pitre wrote:
> > > On Thu, 28 Oct 2010, Russell King - ARM Linux wrote:
> > > 
> > > > On Thu, Oct 28, 2010 at 02:24:33PM -0400, Nicolas Pitre wrote:
> > > > > On Thu, 28 Oct 2010, Daniel Walker wrote:
> > > > > 
> > > > > > This is what the function currently has,
> > > > > > 
> > > > > >         .macro  addruart, rp, rv
> > > > > >         ldr     \rp, =MSM_DEBUG_UART_PHYS
> > > > > >         ldr     \rv, =MSM_DEBUG_UART_BASE
> > > > > >         .endm
> > > > > > 
> > > > > > So if we have a MSM_DEBUG_UART_PHYS and MSM_DEBUG_UART_BASE we're
> > > > > > returning it. We don't actually have those values for all the boards
> > > > > > tho. My understanding was that there are some generic arm changes
> > > > > > needed, but I need to confirm that.
> > > > > 
> > > > > Just return 0 in both registers when you have nothing better to return.
> > > > 
> > > > That's not a good idea - it'll cause 512MB of 1:1 mappings to be setup
> > > > at virtual location 0 using the IO flags, which may conflict on ARMv6+.
> > > > A better idea would be to return 0xfff00000, which'll cause it to only
> > > > populate the top-most 1MB.
> > > 
> > > Given that this a phony address, better test for 0 explicitly and skip 
> > > the mapping as well as bailing out early from putchar, etc.
> > 
> > That could be 0 phys, which given there is no defined memory layout on
> > ARM, I would not put it past someone to put a UART at phys location 0
> > one day.
> 
> Who knows.  But in this case I think it is probably cleaner to just care 
> about the virtual address, and do something like this:

I need something for this merge window (which is closing soon) .. So I'm
just going to go with my original revert .. It seems like anything I do
to get addruart to return something turns into too large a patch which I
don't want to force.

I think the revert should be fine until we come up with a good way to
fix this, either what you suggested or something entirely in msm.

Daniel


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